1. Field of the Invention
This invention relates to a recording head for use as a printing head in an image forming apparatus such a as a printer, a copying apparatus or a facsimile apparatus.
2. Related Background Art
Heretofore, as a recording head of this kind, a solid light emitting element array typified by LEDs (light emitting diodes) is arranged in a row and individual light emitting elements are controlled in conformity with a recording signal to thereby effect recording. Also, in such a recording head, a drive circuit is provided correspondingly to each individual light emitting element of the light emitting element array, and a drive IC in which these drive circuits are integrated is disposed adjacent to the light emitting element array chips and the two chips are connected together by wire bonding. On the other hand, recently, a light emitting element array having the self-scanning function so as to successively select and drive light emitting elements in the array chip is also proposed in U.S. Pat. No. 5,451,977. The use of such a light emitting element array having the self-scanning function can remarkably curtail the number of wirings connecting the light emitting element array and a drive IC together and therefore, when the light emitting element array chip and the drive IC are carried on discrete substrates, it becomes possible to connect the two substrates together by the use of a flexible cable.
Now, if there is adopted such structure that the light emitting element array chip and drive IC of a recording head are carried on discrete substrates and the substrate carrying the light emitting element array chip thereon is opposed to a photosensitive drum, the thickness (height) of the recording head can be made very small and therefore, the use of a photosensitive drum of a smaller diameter becomes possible and thus, it becomes possible to downsize an apparatus such as a printer or a copying apparatus using it. However, when the substrate carrying the light emitting element array chip thereon and the substrate carrying the drive IC thereon, or the substrate carrying the light emitting element array chip thereon and a flexible cable are connected together, there has been the following problem.
When such a substrate and a cable are to be connected together, use is usually made of a connecting method using soldering heat welding, but during the connection, a flux or the like is scattered and adheres to the surface of the light emitting element array chip to thereby cause the deterioration of its characteristics, for example, creating an irregular quantity of emitted light. Therefore, when the substrate and the flexible cable are to be connected together, it is necessary to connect the two together with the tip end of the cable spaced apart relative to the light emitting element array chip on the substrate to a certain degree, and to secure a distance corresponding to the spacing apart, the width of the substrate must be increased in conformity therewith. However, if the width of the substrate for the light emitting element array chip is increased, the recording a head will become correspondingly bulky and therefore, the downsizing of the recording head is limited. Decreasing the width of the substrate carrying the light emitting element array thereon has been a task in further downsizing the recording head.